docs: def get_tgt_for(user):
      """
      Fetch a ticket granting ticket for a given user.
  
      :param user: UserObj
  
      :return: TGT or Exepction
      """
      if not settings.CAS_PROXY_CALLBACK:
          raise CasConfigException("No proxy callback set in settings")
  
      try:
          return Tgt.objects.get(username=user.username)
      except ObjectDoesNotExist:
          logger.warning('No ticket found for user {user}'.format(
              user=user.username
          ))
          raise CasTicketException("no ticket found for user " + user.username)